In the LTE and Long-Term Evolution-Advanced (LTE-A) systems, downlink system resources are divided into two parts, i.e., a control region and a data region. Herein the control region is primarily used for transmitting control signals of a system or a User Equipment (UE), which comprise a Common Reference Signal (CRS), a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), a Physical Downlink Control Channel (PDCCH) or the like. The data region is primarily used for transmitting a Physical Downlink Shared Channel (PDSCH) of the UE.
For the LTE system, one downlink subframe comprises 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols, wherein the first 1-3 OFDM symbols are the control region, and the number of OFDM symbols occupied by the control region is notified by a base station to the UE through the PCFICH channel. Except for the control region, the remaining OFDM symbols are used as the data region to transmit the PDSCH. A diagram of the control region and the data region is shown in FIG. 1.
When the network schedules downlink services of a user and allocates the downlink radio resources, the base station transmits scheduling information to the UE through the PDCCH channel. The resource positions in the scheduling information only comprise positions in the frequency domain allocated to the UE, and in the time domain, resource positions are remaining OFDM symbols excluding the control region by default for the UE. For example, the control region occupies the first 3 OFDM symbols, and then the 4th to 14th OFDM symbols in the time domain belong to the data region by default for the UE, i.e., the data region occupies 11 OFDM symbols.
The coordinated multi-point network in the LTE system refers to that different stations/cells transmit information to the same UE in the LTE system. Different stations/cells may transmit the same information to the same UE for example downlink Joint Transmission (JT) transmission technology in the Coordinated Multi-Point (CoMP). Different stations/cells may also transmit different information to the same UE, for example, one station/cell transmits the PDCCH to a UE, and another station/cell transmits the downlink PDSCH to the UE. The coordinated multi-point network described here refers to a scenario where different stations/cells transmit different information to the same UE, for example, one station/cell transmits the PDCCH to a UE, and another station/cell transmits the PDSCH to the UE. A station/cell which transmits the PDCCH to a UE is referred to as a control station/cell, and a station/cell which transmits the PDSCH to a UE is referred to as a service station/cell. In the coordinated multi-point network, when the station/cell which transmits the PDSCH to the UE doesn't need to transmit a control channel such as the PDCCH or the like, the control region thereof is idle and cannot transmit the PDSCH, which wastes valuable radio resources.
In the LTE-A system, characteristics of carrier aggregation are introduced, and cross-carrier scheduling is allowed, i.e., using the PDCCH transmitted on one carrier to schedule the PDSCH on another carrier. At this time, the PDCCH and the PDSCH of the UE are on different carriers respectively, and a carrier on which the PDCCH is transmitted to the UE is referred to as a control carrier, and a carrier on which the PDSCH is transmitted to the UE is referred to as a service carrier. If the carrier on which the PDSCH is transmitted have no control channel for transmission, the control region thereof is idle, which wastes valuable radio resources.
Further, in order to better ensure transmission quality of control information of the Pico station, an enhanced Physical Downlink Control Channel ePDCCH is introduced in the standard Release 11 (R11) of the 3rd Generation Partnership Project (3GPP). The ePDCCH has the same function and purpose as those of the PDCCH in the standard R8/9 of the 3GPP, and may be used to indicate the scheduling information of the PDSCH or PDSCH of a UE. However, resource positions of the ePDCCH are different from those of the PDCCH/PHICH of the 3GPP standard RS/9 release, and the ePDCCH no longer transmits in the control region of backward compatible carriers, and instead, transmits Downlink Control Information (DCI) information by sharing the data region in the 3GPP standard R8/9 with the PDSCH by means of Frequency Division Multiplexing (FDM); additionally, the ePDCCH also no longer uses a Cell-specific Reference Signal (CRS) for demodulation, and instead, uses a Demodulation Reference Signal (DMRS) for demodulation. The ePDCCH can not only exist in compatible carriers, but also can be a New Carrier Type (NCT) of downlink control channel. When the ePDCCH is used for controlling scheduling, if there is no need to transmit a control channel of another UE in a control region of the cell, the PDSCH also cannot use the resources in control region, and thus there is also a problem of a waste of radio resources.